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From eb79fee19724dcfde162892cfb4b9175a470308a Mon Sep 17 00:00:00 2001
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From: Simon Kelley <simon@thekelleys.org.uk>
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Date: Tue, 5 Dec 2017 22:37:29 +0000
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Subject: [PATCH] Fix infinite retries in strict-order mode.
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If all configured dns servers return refused in
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response to a query; dnsmasq will end up in an infinite loop
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retransmitting the dns query resulting into high CPU load.
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Problem is caused by the dns refuse retransmission logic which does
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not check for the end of a dns server list iteration in strict mode.
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Having one configured dns server returning a refused reply easily
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triggers this problem in strict order mode. This was introduced in
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9396752c115b3ab733fa476b30da73237e12e7ba
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Thanks to Hans Dedecker <dedeckeh@gmail.com> for spotting this
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and the initial patch.
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(cherry picked from commit ef3d137a646fa8309e1ff5184e3e145eef40cc4d)
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---
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src/forward.c | 14 ++++++++++++--
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1 file changed, 12 insertions(+), 2 deletions(-)
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diff --git a/src/forward.c b/src/forward.c
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index 255d6c0..e61cd50 100644
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--- a/src/forward.c
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+++ b/src/forward.c
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@@ -804,10 +804,20 @@ void reply_query(int fd, int family, time_t now)
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unsigned char *pheader;
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size_t plen;
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int is_sign;
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-
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+
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+ /* In strict order mode, there must be a server later in the chain
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+ left to send to, otherwise without the forwardall mechanism,
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+ code further on will cycle around the list forwever if they
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+ all return REFUSED. Note that server is always non-NULL before
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+ this executes. */
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+ if (option_bool(OPT_ORDER))
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+ for (server = forward->sentto->next; server; server = server->next)
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+ if (!(server->flags & (SERV_LITERAL_ADDRESS | SERV_HAS_DOMAIN | SERV_FOR_NODOTS | SERV_NO_ADDR | SERV_LOOP)))
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+ break;
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+
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/* recreate query from reply */
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pheader = find_pseudoheader(header, (size_t)n, &plen, NULL, &is_sign, NULL);
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- if (!is_sign)
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+ if (!is_sign && server)
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{
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header->ancount = htons(0);
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header->nscount = htons(0);
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--
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2.26.2
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